LibCore: Add wrappers for tc{get,set}winsize

On Serenity, this uses the equivalent LibC function, otherwise it
defaults to the pretty standard ioctl equivalent.

At the time of writing, it seems that only musl, BSDs and Serenity have
the standardized POSIX function.

Userland/Libraries/LibCore/System.cpp

@@ -826,6 +826,31 @@ ErrorOr<void> tcsetattr(int fd, int optional_actions, struct termios const& ios)
     return {};
 }
 
+ErrorOr<winsize> tcgetwinsize(int fd)
+{
+    winsize ws {};
+#ifdef AK_OS_SERENITY
+    if (::tcgetwinsize(fd, &ws) < 0)
+        return Error::from_syscall("tcgetwinsize"sv, -errno);
+#else
+    if (::ioctl(fd, TIOCGWINSZ, &ws) < 0)
+        return Error::from_syscall("ioctl"sv, -errno);
+#endif
+    return ws;
+}
+
+ErrorOr<void> tcsetwinsize(int fd, winsize const& ws)
+{
+#ifdef AK_OS_SERENITY
+    if (::tcsetwinsize(fd, &ws) < 0)
+        return Error::from_syscall("tcsetwinsize"sv, -errno);
+#else
+    if (::ioctl(fd, TIOCSWINSZ, &ws) < 0)
+        return Error::from_syscall("ioctl"sv, -errno);
+#endif
+    return {};
+}
+
 ErrorOr<int> tcsetpgrp(int fd, pid_t pgrp)
 {
     int rc = ::tcsetpgrp(fd, pgrp);

Userland/Libraries/LibCore/System.h

@@ -149,6 +149,8 @@ ErrorOr<ByteString> getcwd();
 ErrorOr<void> ioctl(int fd, unsigned request, ...);
 ErrorOr<struct termios> tcgetattr(int fd);
 ErrorOr<void> tcsetattr(int fd, int optional_actions, struct termios const&);
+ErrorOr<winsize> tcgetwinsize(int fd);
+ErrorOr<void> tcsetwinsize(int fd, winsize const&);
 ErrorOr<int> tcsetpgrp(int fd, pid_t pgrp);
 ErrorOr<void> chmod(StringView pathname, mode_t mode);
 ErrorOr<void> lchown(StringView pathname, uid_t uid, gid_t gid);